Method for recovering catalytic wet oxidation catalyst by membrane filtration method

Abstract

The invention discloses a method for recovering a catalytic wet oxidation catalyst by a membrane filtration method, which comprises the following steps: adjusting saline water subjected to catalytic wet oxidation to be alkaline, and carrying out solid-liquid separation by a filter membrane assembly to obtain a treatment liquid and a first solid; the filter membrane assembly adopts the micron-sized ePTFE membrane, so that penetration of a catalyst in a precipitation form can be effectively blocked, and permeated catalyst ions are at a ppb level, so that the filter membrane assembly can directly cross a chelate resin tower. Meanwhile, the filter membrane assembly is provided with a DCS sequential control system, the concentration of the catalyst at the conical bottom of the membrane filter shell can be directly controlled by changing the filtering time length, the back-flushing period, the back-flushing time length and the like and is far higher than the concentration of the catalyst obtained through natural sedimentation, and therefore the defects existing in catalyst recovery in an existing catalytic wet oxidation reaction are overcome. The membrane filtration method disclosed by the invention has great significance in improving the catalyst recovery effect of the catalytic wet oxidation method, can generate considerable economic benefits, and has relatively high popularization and application values.

Description

Technical Field

[0001] The invention belongs to the field of wastewater treatment and relates to a method for recovering a catalytic wet oxidation catalyst by a membrane filtration method. Background Art

[0002] Wet oxidation technology is an effective method for treating toxic and hazardous, high-concentration organic wastewater developed in the 1950s. Domestic research on WAO began in the 1980s. WAO is a process of treating toxic and hazardous, high-concentration organic wastewater with oxygen in the air under high temperature and high pressure. 2 As an oxidant, it oxidizes organic pollutants into CO in the liquid phase 2 and H 2 The chemical process of removing inorganic or organic small molecules such as O. The characteristics of wet oxidation technology are its wide range of applications and its ability to effectively oxidize various types of high-concentration organic wastewater without any selectivity.

[0003] In order to improve the oxidation efficiency of wet oxidation and the decomposition efficiency of organic matter, people have developed catalytic wet oxidation treatment technology using efficient and stable catalysts based on traditional wet oxidation technology. This technology uses oxygen-rich gas or oxygen as the oxidant, and uses the catalytic effect of the catalyst to reduce the activation energy of the wet oxidation reaction, so as to accelerate the reaction between organic matter and the oxidant in the wastewater, thereby oxidizing the organic matter and poisons such as N and S in the wastewater into CO. 2 、N 2 、SO 2 , H 2 O, in order to achieve the purpose of wastewater purification. The catalysts used for catalytic wet oxidation treatment can be divided into homogeneous oxidation catalysts and heterogeneous oxidation catalysts.

[0004] At present, the principle of Fenton reaction is mainly used in catalytic wet oxidation operation to treat organic matter in wastewater. In order to save costs, the homogeneous catalyst of Fenton reaction needs to be recycled. The wastewater after catalytic wet oxidation contains 500-5000ppm of catalyst ions. At present, the recovery of the catalyst in the wastewater adopts the method of precipitation + adsorption of clear liquid with chelating resin + separation of turbid liquid with centrifuge + catalyst re-dissolution for recovery, and the purpose of refining the clear liquid is achieved at the same time. This process realizes the recovery of metal ions in wastewater and the purification of metal ions in refined water through the combination of the above three steps. Among them: step one is to add flocculants to settle in an alkaline environment, so that the metal ions settle in the catalyst settling tank; step two is to use chelating resin to adsorb low-concentration metal ions in the sedimentation clear liquid, and the low-concentration metal ions in the supernatant in the sedimentation tank are acidified by adjusting the pH of the brine to ensure the ionic state of the metal, and then adsorbed and retained by chelating resin to achieve refining, and the resin needs to be regenerated after saturation; step three is to use a high-speed horizontal spiral centrifuge to separate the sedimentation turbid liquid, and the precipitate after centrifugation is dissolved with acid and then reused in the wet oxidation reactor. In actual operation, this process has the following main disadvantages:

[0005] In order to achieve the sedimentation effect, it is necessary to consider factors such as flocculant concentration, system processing capacity, material pH, material temperature, solution salt content, etc., so the operation is difficult. In addition, during the centrifugal separation process, due to the change in sedimentation concentration, the change in the centrifuge load will also cause changes in the centrifugal separation effect, and then cause changes in the catalyst system concentration. In addition, the chelating resin has a high requirement for the pH value, and the alkaline sedimentation clear liquid will cause the pH value of the clear liquid acidification process to be difficult to control due to the change in metal content, which is easy to cause fluctuations, and then cause the metal ion content in the refined brine to exceed the standard. At the same time, the copper ion content in the sedimentation clear liquid is high, and the chelating resin saturation cycle is short, requiring frequent regeneration of the chelating resin, resulting in fluctuations in material consumption and indicators.

[0006] In addition, during the sedimentation process, more flocculants wrap the precipitate and are easy to accumulate in the catalyst, and scale in the storage tanks and pipelines of the catalyst system, causing pipeline blockage and equipment failure. The flocculants in the sedimentation clear liquid will also cause the blockage of the resin pores in the chelating resin tower and the compaction of the resin bed, resulting in an increase in pressure drop and a decrease in adsorption capacity, thereby reducing the flux and adsorption capacity of the resin tower; and compaction will also cause incomplete regeneration, and agglomeration will also cause bridging, resulting in biased flow and short circuit of the resin bed, which will seriously restrict the brine treatment load and indicator stability.

[0007] Furthermore, natural sedimentation is also limited by the sedimentation rate, and the concentration of the settled catalyst is low, while the high-temperature oxidation system needs to maintain a certain catalyst concentration. Therefore, a large amount of catalyst solution needs to be added, otherwise the system's ability to treat organic wastewater will be reduced, thereby reducing the wastewater treatment load. Summary of the invention

[0008] In order to improve the above technical problems, the present invention provides a method for recovering a catalytic wet oxidation catalyst, comprising adjusting the brine after catalytic wet oxidation to alkalinity, performing solid-liquid separation through a filter membrane assembly, and obtaining a treated liquid and a first solid.

[0009] According to an embodiment of the present invention, the catalyst used in the catalytic wet oxidation is copper chloride. Preferably, the concentration of copper ions in the brine after the catalytic wet oxidation is 800-2500 mg / L, preferably 1000-2000 mg / L, and more preferably 1200-1700 mg / L.

[0010] According to an embodiment of the present invention, an alkali solution is added to the brine after catalytic wet oxidation to adjust the pH to 9.5 to 12, exemplified by 9.5, 10.5, 11, and 12. For example, the alkali solution may be a NaOH solution. For another example, the concentration of the NaOH solution is 10 to 30 wt%, exemplified by 10 wt%, 20 wt%, and 30 wt%.

[0011] According to an embodiment of the present invention, the method further comprises: mixing the first solid with an acid to regenerate the catalyst, and recycling the regenerated catalyst to the catalytic wet oxidation. Preferably, the acid is hydrochloric acid. Preferably, the catalyst regeneration is performed in a dissolving tank.

[0012] According to an embodiment of the present invention, the filter membrane assembly includes a mounting plate, a mounting hole, a cylindrical filter membrane and a backwash port. The mounting plate is provided with a plurality of mounting holes, and the cylindrical filter membrane is installed in the mounting holes.

[0013] In one embodiment of the present invention, the cylindrical filter membrane is a micron-sized e-PTFE membrane. Preferably, the pore size of the micron-sized e-PTFE membrane is 0.1 to 0.5 μm, exemplified by 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, and 0.5 μm.

[0014] In one embodiment of the present invention, a cylindrical filtration membrane with a pore size of 0.2 μm is used, and under operating conditions, its membrane flux is 0.278 m3 / m 2 h.

[0015] In one embodiment of the present invention, the operating pressure of the cylindrical filtration membrane is 3 kPa-100 kPa, exemplarily 65 kPa.

[0016] In one embodiment of the present invention, the single filtration time of the cylindrical filtration membrane can be 400 to 800 seconds, exemplarily 600 seconds. The cylindrical filtration membrane of the present invention can perform two consecutive filtrations and then discharge the residue once.

[0017] In one embodiment of the present invention, the backwashing time of the filter membrane assembly is 10s-25s, exemplified by 10s, 15s, 20s, and 25s.

[0018] In one embodiment of the present invention, the backwash period of the filter membrane assembly is 685s.

[0019] In the present invention, the recoil pressure of the filter membrane assembly is the height difference between the clear liquid in the clear liquid buffer area at the top of the membrane filter housing and the inlet of the recoil tank, and the pressure difference generated after overcoming the flow resistance. For example, the recoil pressure is 10kPa-20kPa.

[0020] According to an embodiment of the present invention, a membrane filter housing is provided outside the membrane filter assembly. Preferably, the membrane filter assembly is embedded and installed on the top of the membrane filter housing.

[0021] According to an embodiment of the present invention, a feed inlet is provided on one side of the bottom of the membrane filter housing, and a clear liquid discharge port is provided on one side of the top of the membrane filter housing.

[0022] According to an embodiment of the present invention, an overflow port (backwashing discharge port) is provided at the lower portion of the membrane filter housing, and the overflow port (backwashing discharge port) is connected to the backwashing tank.

[0023] According to an embodiment of the present invention, a filter residue discharge port is provided at the bottom of the membrane filter housing, and a filter residue discharge port is installed with a filter residue discharge valve.

[0024] According to an embodiment of the present invention, the deslagging cycle can be set according to the catalyst concentration in the brine after catalytic wet oxidation and the recoil cycle. For example, the deslagging cycle can be 1470s or 1540s.

[0025] According to an embodiment of the present invention, the slag discharge time can be set according to the catalyst concentration in the brine entering the membrane assembly, for example, it can be 100s-180s, exemplified by 100s, 110s, 120s, 130s, 140s, 150s, 160s, 170s, and 180s.

[0026] In the present invention, after the brine after catalytic wet oxidation is adjusted to alkalinity, it is fed into the interior of the membrane filter housing through the feed port, solid-liquid separation is carried out through the cylindrical filter membrane, copper hydroxide precipitates are adsorbed on the surface of the cylindrical filter membrane, and the clear liquid passes through the cylindrical filter membrane and is discharged from the clear liquid discharge port; when the filtration pressure difference is too large, does not meet the flow requirement or exceeds the tolerance pressure of the cylindrical filter membrane, backwashing is carried out through the backwashing pipeline, and the copper hydroxide precipitate filter cake adsorbed on the surface of the cylindrical filter membrane is backwashed with the clear liquid in the clear liquid buffer zone at the top of the membrane filter housing, the clear liquid after backwashing flows back to the backwashing tank and then flows back to the initial feed unit, and the copper hydroxide precipitates flushed down freely settle to the bottom of the membrane filter housing, and are discharged through the filter residue discharge port at the bottom of the membrane filter housing, and are sent to the catalyst dissolution tank for dissolution and regeneration, and then recycled to the oxidation reactor for repeated use.

[0027] According to an embodiment of the present invention, lifting ears are arranged around the middle of the membrane filter housing.

[0028] According to an embodiment of the present invention, a pressure gauge is installed on one side of the top of the membrane filter housing.

[0029] According to an embodiment of the present invention, the mounting plate is a disc-shaped structure. Preferably, the mounting plate is made of titanium or other acid- and alkali-resistant materials with high structural strength.

[0030] According to an embodiment of the present invention, the membrane filter assembly is further provided with a DCS control system. The DCS control system realizes automatic control, and the parameters such as the filtration time, the recoil cycle, and the recoil time of the membrane filter assembly can be adjusted according to the catalyst concentration in the brine after the catalytic wet oxidation and the production load.

[0031] In the present invention, the control method of the DCS control system is as follows: when the cylindrical filter membrane is acid-washed and the catalyst is regenerated (new membrane operation), it starts to operate (the initial pressure difference is 3 kPa, and the operation time can be set according to the catalyst concentration in the brine entering the filter membrane assembly), when the operation time reaches the set value and / or the filter cake (the first solid) gradually accumulates until the operation pressure difference reaches about 65 kPa, the cylindrical filter membrane stops filtering (the single filtration operation time of the cylindrical filter membrane is generally set to 600 s) due to the transmission resistance and / or the strength of the cylindrical filter membrane, and starts backwashing (backwashing time 25s), after the backwashing is completed, it returns to the initial pressure difference and proceeds to the next filtration cycle. After two filtrations, a 180s slag discharge is performed; after a long period of operation, if the DCS control system detects that the backwashing cannot restore the cylindrical filter membrane to the initial pressure difference and / or the time taken to run to the maximum allowable pressure difference is too short, and the equipment operation cycle cannot meet the production needs, then acid washing is started to remove the filter cake (the first solid) or other impurities in the pores of the cylindrical filter membrane that cannot be removed by backwashing (the solution after acid washing can be re-prepared as a catalyst), and the cylindrical filter membrane after acid washing is put into operation again.

[0032] The present invention also provides a catalyst obtained by the above method.

[0033] The present invention also provides the use of the above method in treating wastewater by catalytic wet oxidation, preferably in recovering catalysts from wastewater by catalytic wet oxidation.

[0034] The present invention also provides a method for treating wastewater by catalytic wet oxidation, wherein the catalyst is recovered by the above method.

[0035] Beneficial effects of the present invention:

[0036] (1) The present invention uses a filter membrane assembly to recover the catalyst in the catalytic wet oxidation. It only needs to adjust the pH of the brine after the catalytic wet oxidation to 9.5-12, so that the copper ions in the catalytic wet oxidation catalyst are converted into copper hydroxide flocculent precipitation. The solid-liquid separation of the filter membrane assembly can effectively intercept the copper hydroxide flocculent precipitation in the brine and allow water and NaCl dissolved in the water to pass through, while the copper hydroxide flocculent precipitation is blocked on the outside of the membrane. After the filter cake is formed, the filter cake is recoiled to fall off the membrane surface. The fallen filter cake can quickly settle to the bottom of the cone of the membrane filter housing due to its heavy unit mass. By opening the slag discharge valve at the bottom of the cone, the precipitate returns to the catalyst dissolution tank for dissolution and regeneration and then is reused in the oxidation reactor. The filter membrane assembly of the present invention uses a micron-level ePTFE membrane, which has a larger processing capacity than a precision filter with a nanometer pore size, a lower operating pressure, and no additional power facilities are added, thereby saving power consumption and reducing equipment requirements. The content of each metal ion in the water treated by the method of the present invention is as low as 50-100 ppb, so it fully meets the reuse standard of the chlor-alkali device.

[0037] (2) The catalyst is recovered by the method of the present invention without adding a flocculant, and the filter membrane assembly of the present invention uses a micron-grade ePTFE membrane to effectively block the penetration of the catalyst in the precipitated form, so that the catalyst ions that penetrate through are at the ppb level, meeting the index requirements, and thus can directly cross the chelating resin tower. At the same time, the filter membrane assembly of the present invention is provided with a DCS sequential control system, which can directly control the catalyst concentration at the bottom of the cone of the membrane filter housing by changing the filtration time, recoil cycle, recoil time, etc., and is much higher than the catalyst concentration obtained by natural sedimentation, thereby solving the drawbacks of the catalyst recovery in the existing catalytic wet oxidation reaction. The membrane filtration method of the present invention is of great significance to improving the catalyst recovery effect of the catalytic wet oxidation method, can produce considerable economic benefits, and has a high promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the overall structure of the filter membrane assembly of the present invention;

[0039] Figure 2 is a side view of the filter membrane assembly;

[0040] Figure 3 is a top view of the filter membrane assembly;

[0041] Figure 4 The process flow chart of recovering the catalytic wet oxidation catalyst by the membrane filtration method of the present invention;

[0042] Figure 5 This is the surface state diagram of the cylindrical filter membrane after 1300 minutes of filtration;

[0043] Figure 6 This is the surface state diagram of the cylindrical filter membrane after acid washing after 1300 minutes of filtration operation;

[0044] Figure 7 The Cu content in the filtered clear solution after the cylindrical membrane filtration was run for 1300 minutes 2+ and other metal ion contents (μg / L);

[0045] Numbers in the figure: 1, membrane filter housing; 2, feed inlet; 3, filter membrane assembly; 4, clear liquid outlet; 5, overflow port; 6, first slip-on flange; 7, connecting pipe; 8, second slip-on flange; 9, recoil tank; 10, mounting plate; 11, mounting hole; 12, cylindrical filter membrane; 13, backwash port. DETAILED DESCRIPTION

[0046] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0047] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0048] Example 1

[0049] The wastewater (with a salt content of 19wt%, a TOC concentration of 3500mg / L, and a pH of 12) generated from the saponification process of the epichlorohydrin device is subjected to catalytic wet oxidation to obtain a brine (with a salt content of 19wt%, a pH of 1, and a copper ion content of 1722008μg / L). A caustic soda solution with a concentration of 20wt% is used to adjust the pH of the brine to 11 so that the copper ions in the brine are converted into copper hydroxide precipitates. The brine is fed into the interior of the membrane filter housing 1 through the feed port 2 by a feed pump. The brine entering the membrane filter housing 1 is filtered through a cylindrical filter membrane 12 (using an ePTFE membrane with a pore size of 0.2μm, the operating pressure is increased from 3kPa to 65kPa, and the filtration time is 600s). The copper hydroxide precipitate is adsorbed on the surface of the cylindrical filter membrane 12, and the qualified clear liquid is discharged from the clear liquid discharge port 4 through the cylindrical filter membrane 12 and buffered in the clear liquid buffer area at the top of the membrane filter housing 1. The feed pump is turned off, and the shut-off valve between the overflow port 5 and the recoil tank 9 is opened instantaneously. The clear liquid in the clear liquid buffer area on the top of the membrane filter housing 1 uses the liquid level difference to backwash the copper hydroxide precipitate adsorbed on the surface of the cylindrical filter membrane 12 (the backwash pressure difference is about 10 kPa, the recoil time is 25 s, and the recoil cycle is 685 s). The copper hydroxide precipitate filter cake on the cylindrical filter membrane 12 is washed down by backwashing and freely settles to the bottom of the membrane filter housing 1, and is discharged through the slag discharge port at the bottom of the membrane filter housing 1 (the slag discharge cycle is 1470 s, and the slag discharge time is 110 s) and sent to the catalyst dissolution tank. The regenerated catalyst is obtained after dissolving with 30 wt % concentrated hydrochloric acid. The regenerated catalyst is recovered to the catalytic wet oxidation reactor for repeated use.

[0050] The Cu in the clear liquid discharged from the clear liquid outlet 4 after filtration 2+ The contents of other metal ions (μg / L) are shown in Table 1 below.

[0051] Table 1

[0052]

[0053] Example 2

[0054] Compared with Example 1, the only difference is that: the pH of the brine is adjusted to 12 using a caustic soda solution with a concentration of 20wt%; the copper ion feed concentration is 2023000μg / L, and the rest is the same as Example 1.

[0055] The Cu in the clear liquid discharged from the clear liquid outlet 4 after filtration 2+ The contents of other metal ions (μg / L) are shown in Table 2 below.

[0056] Table 2

[0057]

[0058] Example 3

[0059] Compared with Example 1, the difference is that: the pH of the brine is adjusted to 9.5 using a caustic soda solution with a concentration of 20wt%; the copper ion feed concentration is 1223000μg / L, and the rest is the same as Example 1.

[0060] The Cu in the clear liquid discharged from the clear liquid outlet 4 after filtration 2+ The contents of other metal ions (μg / L) are shown in Table 3 below.

[0061] Table 3

[0062]

[0063]

[0064] The above experimental results show that after filtration by the cylindrical filter membrane of the present invention, the copper ion concentration in the brine after catalytic wet oxidation can be reduced from 2000ppm to below 100ppb. Too high a pH value will shorten the recoil cycle, reduce the processing capacity of the cylindrical filter membrane, and cause waste of alkali solution, increasing the cost of catalyst recovery; but when the pH is lower than 9, the flocculent precipitation formed by copper ions will block the membrane pores and cannot be removed by recoil, thereby reducing the processing capacity of the cylindrical filter membrane.

[0065] Example 4

[0066] The cylindrical filter membrane was operated during the daytime from July 8 to July 26, 2024 (operating conditions were the same as those in Example 1), with a total filtration time of 1300 minutes and a total filtration volume of about 6.6 m3. After the cylindrical filter membrane was operated for up to 1 hour, the Cu content of the clear liquid discharged from the clear liquid outlet 4 was measured. 2+ and other metal ion contents (μg / L), the results are as follows Figure 7As shown in the figure, it can be seen that the cylindrical filtration membrane of the present invention has a good and stable separation and recovery effect on copper hydroxide. After continuous operation and filtration, the copper ions in the clear liquid are all below 40 ppb, and the contents of other ions are all within the range of the effluent index of the refined brine in the epichlorohydrin section, and the effluent quality is stable.

[0067] Figure 5 This is the surface state diagram of the cylindrical filter membrane after 1300 minutes of filtration. It can be seen from the figure that a very thin layer of filter cake is deposited on the surface of the cylindrical filter membrane.

[0068] Figure 6 This is a surface state diagram of the cylindrical filter membrane after being pickled with 10wt% hydrochloric acid after filtration operation for 1300 minutes. It can be seen from the figure that the surface of the cylindrical filter membrane is restored to its original state after pickling, and the pickling effect is obvious. It can be used again for catalyst recovery and can be reused to reduce wastewater treatment costs. It has considerable economic benefits and promotion and application value.

[0069] Example 5

[0070] The cylindrical filter membrane after filtration in Example 1 was soaked in high-concentration epichlorohydrin saponified wastewater (TOC concentration of organic matter was 3500 ppm) for one week, and the cylindrical filter membrane after soaking was filtered again according to the method in Example 1. 2+ The concentration is less than 100 ppb, which indicates that the cylindrical filtration membrane of the present invention has tolerance to organic wastewater below 3500 ppm and has excellent ability to resist production abnormalities.

[0071] In summary, compared with nanofiltration membranes, the filter membrane assembly of the present invention only requires an operating pressure of less than 100 kPa, so it has low requirements for equipment and low energy consumption, and the water quality of the effluent (low metal ion content) is significantly better than the existing nanofiltration membrane filtration method; at the same time, the present invention adopts an e-PTFE filter membrane, which is resistant to organic swelling, so the filter membrane assembly of the present invention has lower requirements for the inlet water quality (TOC content) than the nanofiltration membrane (industrial verification shows that the cylindrical filter membrane of the present invention can tolerate epichlorohydrin saponification wastewater with TOC < 3500 ppm), so it can be suitable for catalyst recovery treatment of wastewater with different TOC contents, and has broad application prospects.

[0072] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for recovering a catalytic wet oxidation catalyst, characterized in that: The method comprises adjusting the brine after catalytic wet oxidation to alkalinity, performing solid-liquid separation through a filter membrane assembly, and obtaining a treated liquid and a first solid.

2. The method according to claim 1, characterized in that The catalyst used in the catalytic wet oxidation is cupric chloride. Preferably, the concentration of copper ions in the brine after the catalytic wet oxidation is 800-2500 mg / L, preferably 1000-2000 mg / L. Preferably, an alkali solution is added to the brine after catalytic wet oxidation to adjust the pH to 9.5 to 12. For example, the alkali solution may be a NaOH solution. Preferably, the concentration of the NaOH solution is 10-30 wt%.

3. The method according to claim 1 or 2, characterized in that The method further comprises: mixing the first solid with an acid to regenerate the catalyst, and recycling the regenerated catalyst to the catalytic wet oxidation. Preferably, the acid is hydrochloric acid.

4. The method according to any one of claims 1 to 3, characterized in that: The filter membrane assembly comprises a mounting plate, a mounting hole, a cylindrical filter membrane and a backwashing port. A plurality of mounting holes are provided on the mounting plate, and the cylindrical filter membrane is installed in the mounting holes. Preferably, the cylindrical filter membrane is a micron-sized e-PTFE membrane. Preferably, the pore size of the micron-sized e-PTFE membrane is 0.1-0.5 μm. Preferably, the operating pressure of the cylindrical filtration membrane is 3 kPa-100 kPa, exemplarily 65 kPa. Preferably, the single filtration time of the cylindrical filtration membrane can be 400 to 800 seconds. Preferably, the backwashing time of the filter membrane assembly is 10s-25s. Preferably, the recoil pressure is 10 kPa-20 kPa.

5. The method according to any one of claims 1 to 4, characterized in that: A membrane filter housing is disposed outside the membrane filter assembly. Preferably, the membrane filter assembly is embedded and installed on the top of the membrane filter housing. Preferably, a feed inlet is provided on one side of the bottom of the membrane filter housing, and a clear liquid discharge port is provided on one side of the top of the membrane filter housing. Preferably, an overflow port (backwashing discharge port) is provided at the lower portion of the membrane filter housing, and the overflow port (backwashing discharge port) is connected to a backwashing tank. Preferably, a residue discharge port is provided at the bottom of the membrane filter housing, and a residue discharge valve is installed on the residue discharge port.

6. The method according to any one of claims 1 to 5, characterized in that: The slag discharge time is 100s-180s.

7. The method according to any one of claims 1 to 6, characterized in that: Lifting ears are arranged around the middle of the membrane filter housing. Preferably, a pressure gauge is installed on one side of the top of the membrane filter housing. Preferably, the mounting plate is a disc-shaped structure. Preferably, the filter membrane assembly is also provided with a DCS control system.

8. The catalyst obtained by the method according to any one of claims 1 to 7.

9. Use of the method according to any one of claims 1 to 7 in treating wastewater by catalytic wet oxidation, preferably in recovering catalysts from wastewater by catalytic wet oxidation.

10. A method for treating wastewater by catalytic wet oxidation, wherein the catalyst is recovered by the method according to any one of claims 1 to 7.

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